This invention relates to an apparatus for removing plates from a stack of plates one at a time and depositing them at another location for further processing, and in particular to the gripping head and vacuum supply system associated with such an apparatus.
In many industrial applications it is necessary to remove plates from a stack of plates one at a time and deposit them serially at a remote location for further processing. With rigid plates, such as the lead plates used in storage batteries, it is necessary to separate each plate from the stack before starting to move it away from the stack. This is because the apparatus typically used for moving the plates is a rotary carrier, and as a plate is rotated with the carrier its lower edge strikes the remaining plates in the stack unless it first is separated from the stack. In many applications this separation can be accomplished with a feed apparatus such as shown in U.S. Pat. No. 4,462,745. However, in two situations this prior art device does not function adequately.
First, the apparatus shown in U.S. Pat. No. 4,462,745 uses vacuum alone to pull the forwardmost plate away from the remaining plates in the stack. However, the plates used on large batteries are quite heavy and it may not be possible to generate enough force with vacuum to pull them far enough away from the stack.
Secondly, the apparatus shown in U.S. Pat. No. 4,462,745 utilizes a solenoid valve to initiate vacuum flow to the pick-up head when the head is aligned with the stack and to terminate vacuum flow when it is time to disengage the plate. While solenoid valves are expensive and require periodic maintenance to operate well, they are satisfactory in the single head machine disclosed in the above-referenced prior art patent. However, single head machines are speed limited, since it is not possible to keep a plate adhered to a carrier which is rotating at a high rate of speed. Therefore, in order to increase the feed rate of this type of carrier it is necessary to use multiple heads and when this occurs solenoid valves become overly expensive and troublesome. In addition, use of solenoid valves for machines with high feed rates presents timing problems which increase the cost of the machine and reduce its dependability.
The present invention overcomes the foregoing shortcomings and limitations of the prior art plate feed apparatus by providing a rotary carrier which is comprised of a spaced-apart pair of cylindrical carrier plates which rotate together as a unit on a common axle. Extending between the carrier plates, at three equally-spaced radial locations, are hollow rectangular mounting blocks. Mounted on each of the mounting blocks is a gripping head which is semi-spherical and has a concave gripping surface which faces outwardly from the periphery of the carrier plates. The gripping face has a plurality of ribs extending from it to prevent bending of the plates being held on it. The gripping head is oriented such that it is flush with the forwardmost plate in the stack when it becomes aligned with it. The gripping head is attached to the mounting block through a hollow bellows, and a hole located in the gripping head fluidly interconnects through the bellows with the passageway located in the mounting block.
The gripping head is made from a firm synthetic rubber material and thus is deflectable. However, the gripping head is nonsymmetrical about the hole located in it and, as a result, its leading edge is considerably stiffer than its trailing edge. Since the leading edge is stiff it is not easily deflected, and thus a good seal is formed between the gripping head and the plate. However, since the trailing edge is relatively flexible it will give if the bottom of the plate being carried by it strikes the remaining plates in the stack, and thereby prevent the plate from easily becoming dislodged from the gripping head. The bellows is sufficiently stiff that it remains in an expanded position at the vacuum levels which are created when air is being drawn through it, but collapses when the gripping head contacts a plate and a higher vacuum level is achieved. Thus, once a plate is grasped by a gripping head the bellows collapses and the plate is pulled away from the stack.
In addition, a roller extends between the carrier plates in front of each gripping head. The roller extends outwardly from the periphery of the gripping head and thus moves the stack of plates away from the gripping head as the gripping head approaches the stack. This not only ensures that the leading edge of the gripping head does not interfere with the stack but also creates a small gap between the stack and the gripping head when they become aligned. The vacuum then pulls the forwardmost plate across this small gap thereby adding to the separation caused by the collapsing of the bellows.
Vacuum airflow is provided at the passageways in the mounting blocks through openings which are located in one of the carrier plates, with one opening being aligned with each of the mounting blocks. A first sector plate, which is journaled on the carrier axle but does not rotate with it, has an annular slot extending through it which overlies the openings in the carrier plate when they are radially aligned. A second sector plate, which overlies the first sector plate and is attached to it, has a hole extending through it which opens into the slot in the first sector plate. Finally, a tube, which is connected to a vacuum source, fits into the hole in the second sector plate. Thus, when each opening in the carrier plate first passes over the slot in the first sector plate, vacuum flow is initiated to the gripping head associated with that opening, and when it passes away from the slot vacuum flow is terminated. The slots are located such that the former occurs when the gripping head is aligned with the stack of plates and the latter occurs when the gripping head is at the location where the plates are to be released.
Accordingly, it is a principal object of the present invention to provide a rotary plate feed apparatus which mechanically pulls the forwardmost plate away from the remaining plates in the stack.
It is a further object of the present invention to provide such an apparatus where this pulling action occurs automatically when the plates become affixed to the gripping head which holds them as they are being transported away from the stack.
It is a still further object of the present invention to provide such an apparatus in which low of vacuum to the gripping head is initiated and terminated without the use of solenoid valves.
It is a further object of the present invention to provide such an apparatus in which the timing of vacuum flow to the gripping head results directly from the rotation of the plate feed carrier.
The foregoing and other objectives, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.